As for dramas, movies, and sports images, many clipped images, such as their trailers or highlight images related to their original images exist on the Internet. When it comes to uploading various images on the Internet sites, such as Facebook, Youtube, etc., a lot of users often edit a single original image and then upload the results. As such, the images edited from the same original image and uploaded by the user are provided by a plurality of contents providers, and thus a lot of similar images are provided in a network. In the meantime, analysis of patterns of users using image content in a network shows that it is more likely for the users to watch drama series, teaser trailers, sports game highlights with a lot of similar images in similar time zones.
Many images provided in a network are determined as the same images to the naked eye of a human, but the images often have different binary data in reality. As such, images looking the same to the naked eye but having different binary data are called “logically identical” images.
The reasons why the logically identical images are generated are as follows:
Firstly, the existing image encoding scheme is designed to maximize compression ratio in an image. Secondly, even if multiple uses upload the same images, operators such as Facebook, Youtube may perform self encoding on the images uploaded by the users depending on their own circumstances, and repetition of the encoding may cause the logically identical images. Thirdly, in a case of performing image encoding according to a multi-thread based image encoding scheme for loss compression, a phenomenon of thread synchronization between threads that encode respective frames that make up an image occurs, and the thread synchronization phenomenon causes the logically identical images because even the same images for encoding have different binary information. Fourthly, in a case of an encoding scheme to insert an I frame, a reference for image decoding, at regular intervals, in image editing, the position of the I frame in an original image and the position of the I frame in an edited image may be different. If the position of the I frame is changed, information about other frames that refer to the I frame is changed and binary information of the respective images is changed, thereby causing logically identical images.